The purpose of this conference is to assemble a group of scientists who are involved in pivotal research on the relationship between clonal senescence and differentiation. The conference will begin with an introductory lecture on "The mammalian cell cycle" (A. Pardee) and will be followed by nine sessions targeted at mechanisms of senescence and differentiation. The titles and chairs of the sessions include: Yeast Replication and Differentiation (S. Reed), DNA Replication (M. DePamphilis), Growth Factors and Receptors (G. Carpenter), Signal Transduction (A. Means), Extracellular Matrix (M. Bissell), Tumor Suppressor Genes (G. Stein), Differentiation and Senescence (B. Gilchrest), Summary Lecture (R.Baserga), and Senescence (S. Goldstein). Funds are requested to defray expenses of invited speakers and of junior investigators who might otherwise not be able to attend the meeting and who would present posters at two afternoon sessions. It is anticipated that participants will exchange recent molecular genetic data and develop concepts regarding similarities and differences between clonal senescence and differentiation. Therefore, important insights should be obtained on the normal processes of growth, development and biological aging as well as derangements in these processes that lead to common age-dependent diseases, most notably atherosclerosis and neoplasia.